#!/bin/bash
if [ -n "$1" ] && [ -n "$2" ]; then
   num1="$1"; num2="$2"
else
   read -p "请输入第一个数字: " num1
   read -p "请输入第二个数字: " num2
fi
sum=$(expr $num1 + $num2)
echo "结果是: $sum"
